This invention relates to an exhaust system for a multi-cylinder engine and more particularly to an improved cylinder block, exhaust manifold arrangement for a multi-cylinder engine and particularly one of the V-type.
It is well known in conjuction with certain types of internal combustion engines, particularly the two cycle type as applied for the propulsion unit of a marine outboard drive such as an outboard motor, to form the exhaust manifold within the cylinder block where the exhaust ports and exhausts passages are cast. Although this arrangement has the advantage of simplicity and compactness, the performance of an engine may be changed significantly by changing the point where the exhaust ports merge into exhaust manifold. That is, the length of this distance to the juncture can, if appropriately selected, significantly improve the performance of an engine. However, where the manifold and exhaust ports are formed integrally within the cylinder block it is difficult to obtain the desired length changes. Furthermore, once an engine is built in this manner, it is impossible to change the length of the passages to suit specific applications.
It is, therefore, a principle object of this invention to provide an improved exhaust system for an engine.
It is a further object of this invention to provide an exhaust system for an engine including a manifold that is formed separately from the cylinder block so as to permit length changes for tuning purposes.
It is a still further object to this invention to provide an improved cylinder block manifold arrangement for a two cycle internal combustion engine of the type employed in an outboard motor.